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Ngozi caldera is the most prominent volcanic feature of the Poroto Ridge, a transverse structure at the northern end of the Karonga basin. The trachytic-to-phonolitic volcano contains a 3-km-wide caldera with a 1.5 x 2.5 km lake in the southern part of the caldera that is bounded by steep-walled cliffs 150-300 m high. Numerous pyroclastic cones are situated along the ridge. Eruption of the Kitulo Pumice, radiocarbon dated at about 10,200 cal. years before present, is though to be related to formation of the caldera. The youngest activity appears to have originated from the caldera and from youthful-looking pyroclastic cones to the north; the youngest known eruption produced a pyroclastic flow that swept at least 10 km S about 500 years ago.
Summary of Holocene eruption dates and Volcanic Explosivity Indices (VEI).
|Start Date||Stop Date||Eruption Certainty||VEI||Evidence||Activity Area or Unit|
|1450 ± 40 years||Unknown||Confirmed||Radiocarbon (corrected)|
|8250 BCE (?)||Unknown||Confirmed||5||Radiocarbon (corrected)||Kitulo Pumice|
This compilation of synonyms and subsidiary features may not be comprehensive. Features are organized into four major categories: Cones, Craters, Domes, and Thermal Features. Synonyms of features appear indented below the primary name. In some cases additional feature type, elevation, or location details are provided.
|Feature Name||Feature Type||Elevation||Latitude||Longitude|
|Tangano||Shield volcano||2146 m||8° 58' 0" S||33° 32' 0" E|
|Lake-filled Ngozi caldera is seen here from its southern rim. The 1.5 x 2.5 km caldera lake is bounded by steep-walled cliffs 150-300 m high. The trachytic-to-phonolitic caldera is the most prominent volcanic feature of the Poroto Ridge, a transverse structure at the northern end of the Karonga basin in SW Tanzania. Numerous pyroclastic cones are situated along the ridge. The youngest activity along the ridge appears to have originated from Ngozi caldera and from youthful-looking pyroclastic cones to the north.
Photo by David Williamson, CNRS, France.
The following references have all been used during the compilation of data for this volcano, it is not a comprehensive bibliography. Discussion of another volcano or eruption (sometimes far from the one that is the subject of the manuscript) may produce a citation that is not at all apparent from the title.
Ebinger C J, Deino A L, Drake R E, Tesha A L, 1989. Chronology of volcanism and rift basin propagation: Rungwe volcanic province, East Africa. J Geophys Res, 94: 15,785-15,803.
Fontijn K, Ernst G G J, Elburg M A, Williamson D, Abdallah E, Kwelwa S, Mbede E, Jacobs P, 2010. Holocene explosive eruptions in the Rungwe Volcanic Province, Tanzania . J Volc Geotherm Res, 196: 91-110.
Harkin D A, 1960. The Rungwe volcanics at the northern end of Lake Nyasa. Geol Surv Tanganyika Mem, 2: 1-172.
IAVCEI, 1973-80. Post-Miocene Volcanoes of the World. IAVCEI Data Sheets, Rome: Internatl Assoc Volc Chemistry Earth's Interior..